RE: [PATCH v7 1/1] baseband/acc100: add detection for deRM corner cases

["Chautru, Nicolas" <nicolas.chautru@intel.com>]

Hi Maxime, 

> -----Original Message-----
> From: Maxime Coquelin <maxime.coquelin@redhat.com>
> Sent: Thursday, November 3, 2022 7:10 AM
> To: Vargas, Hernan <hernan.vargas@intel.com>; dev@dpdk.org;
> gakhil@marvell.com; trix@redhat.com
> Cc: Chautru, Nicolas <nicolas.chautru@intel.com>; Zhang, Qi Z
> <qi.z.zhang@intel.com>
> Subject: Re: [PATCH v7 1/1] baseband/acc100: add detection for deRM corner
> cases
> 
> 
> 
> On 11/1/22 05:13, Hernan Vargas wrote:
> > Add function to detect if de-ratematch pre-processing is recommended
> > for SW corner cases.
> > Some specific 5GUL FEC corner cases may cause unintended back pressure
> > and in some cases a potential stability issue on the ACC100.
> > The PMD can detect such code block configuration and issue an info
> > message to the user.
> >
> > Signed-off-by: Hernan Vargas <hernan.vargas@intel.com>
> > ---
> >   drivers/baseband/acc/acc_common.h     |  8 ++++
> >   drivers/baseband/acc/rte_acc100_pmd.c | 55
> +++++++++++++++++++++++++--
> >   2 files changed, 60 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/baseband/acc/acc_common.h
> > b/drivers/baseband/acc/acc_common.h
> > index eae7eab4e9..6213b0b61e 100644
> > --- a/drivers/baseband/acc/acc_common.h
> > +++ b/drivers/baseband/acc/acc_common.h
> > @@ -123,6 +123,14 @@
> >   #define ACC_HARQ_ALIGN_64B          64
> >   #define ACC_MAX_ZC                  384
> >
> > +/* De-ratematch code rate limitation for recommended operation */
> > +#define ACC_LIM_03 2  /* 0.03 */ #define ACC_LIM_09 6  /* 0.09 */
> > +#define ACC_LIM_14 9  /* 0.14 */ #define ACC_LIM_21 14 /* 0.21 */
> > +#define ACC_LIM_31 20 /* 0.31 */ #define ACC_MAX_E (128 * 1024 - 2)
> > +
> >   /* Helper macro for logging */
> >   #define rte_acc_log(level, fmt, ...) \
> >   	rte_log(RTE_LOG_ ## level, RTE_LOG_NOTICE, fmt "\n", \ diff --git
> > a/drivers/baseband/acc/rte_acc100_pmd.c
> > b/drivers/baseband/acc/rte_acc100_pmd.c
> > index 23bc5d25bb..47609f95b7 100644
> > --- a/drivers/baseband/acc/rte_acc100_pmd.c
> > +++ b/drivers/baseband/acc/rte_acc100_pmd.c
> > @@ -756,6 +756,14 @@ acc100_queue_setup(struct rte_bbdev *dev,
> uint16_t queue_id,
> >   		ret = -ENOMEM;
> >   		goto free_lb_out;
> >   	}
> > +	q->derm_buffer = rte_zmalloc_socket(dev->device->driver->name,
> > +			RTE_BBDEV_TURBO_MAX_CB_SIZE * 10,
> > +			RTE_CACHE_LINE_SIZE, conf->socket);
> > +	if (q->derm_buffer == NULL) {
> > +		rte_bbdev_log(ERR, "Failed to allocate derm_buffer memory");
> > +		ret = -ENOMEM;
> > +		goto free_companion_ring_addr;
> > +	}
> >
> >   	/*
> >   	 * Software queue ring wraps synchronously with the HW when it
> > reaches @@ -776,7 +784,7 @@ acc100_queue_setup(struct rte_bbdev *dev,
> uint16_t queue_id,
> >   	q_idx = acc100_find_free_queue_idx(dev, conf);
> >   	if (q_idx == -1) {
> >   		ret = -EINVAL;
> > -		goto free_companion_ring_addr;
> > +		goto free_derm_buffer;
> >   	}
> >
> >   	q->qgrp_id = (q_idx >> ACC100_GRP_ID_SHIFT) & 0xF; @@ -804,6
> +812,9
> > @@ acc100_queue_setup(struct rte_bbdev *dev, uint16_t queue_id,
> >   	dev->data->queues[queue_id].queue_private = q;
> >   	return 0;
> >
> > +free_derm_buffer:
> > +	rte_free(q->derm_buffer);
> > +	q->derm_buffer = NULL;
> >   free_companion_ring_addr:
> >   	rte_free(q->companion_ring_addr);
> >   	q->companion_ring_addr = NULL;
> > @@ -890,6 +901,7 @@ acc100_queue_release(struct rte_bbdev *dev,
> uint16_t q_id)
> >   		/* Mark the Queue as un-assigned */
> >   		d->q_assigned_bit_map[q->qgrp_id] &= (0xFFFFFFFFFFFFFFFF -
> >   				(uint64_t) (1 << q->aq_id));
> > +		rte_free(q->derm_buffer);
> >   		rte_free(q->companion_ring_addr);
> >   		rte_free(q->lb_in);
> >   		rte_free(q->lb_out);
> > @@ -3111,10 +3123,41 @@ harq_loopback(struct acc_queue *q, struct
> rte_bbdev_dec_op *op,
> >   	return 1;
> >   }
> >
> > +/* Assess whether a work around is recommended for the deRM corner
> > +cases */ static inline bool derm_workaround_recommended(struct
> > +rte_bbdev_op_ldpc_dec *ldpc_dec, struct acc_queue *q) {
> > +	if (!is_acc100(q))
> > +		return false;
> > +	int32_t e = ldpc_dec->cb_params.e;
> > +	int q_m = ldpc_dec->q_m;
> > +	int z_c = ldpc_dec->z_c;
> > +	int K = (ldpc_dec->basegraph == 1 ? ACC_K_ZC_1 : ACC_K_ZC_2) * z_c;
> > +	bool recommended = false;
> > +
> > +	if (ldpc_dec->basegraph == 1) {
> > +		if ((q_m == 4) && (z_c >= 320) && (e * ACC_LIM_31 > K * 64))
> > +			recommended = true;
> > +		else if ((e * ACC_LIM_21 > K * 64))
> > +			recommended = true;
> > +	} else {
> > +		if (q_m <= 2) {
> > +			if ((z_c >= 208) && (e * ACC_LIM_09 > K * 64))
> > +				recommended = true;
> > +			else if ((z_c < 208) && (e * ACC_LIM_03 > K * 64))
> > +				recommended = true;
> > +		} else if (e * ACC_LIM_14 > K * 64)
> > +			recommended = true;
> > +	}
> > +
> > +	return recommended;
> > +}
> > +
> >   /** Enqueue one decode operations for ACC100 device in CB mode */
> >   static inline int
> >   enqueue_ldpc_dec_one_op_cb(struct acc_queue *q, struct
> rte_bbdev_dec_op *op,
> > -		uint16_t total_enqueued_cbs, bool same_op)
> > +		uint16_t total_enqueued_cbs, bool same_op,
> > +		struct rte_bbdev_queue_data *q_data)
> >   {
> >   	int ret;
> >   	if (unlikely(check_bit(op->ldpc_dec.op_flags,
> > @@ -3168,6 +3211,12 @@ enqueue_ldpc_dec_one_op_cb(struct acc_queue
> *q, struct rte_bbdev_dec_op *op,
> >   	} else {
> >   		struct acc_fcw_ld *fcw;
> >   		uint32_t seg_total_left;
> > +
> > +		if (derm_workaround_recommended(&op->ldpc_dec, q)) {
> > +			RTE_SET_USED(q_data);
> Why do we need q_data if it is not being used?

As you can guess this notably allows customer do consider running deRM from here as a local patch hence keeping the q_data accessible.
Basically we keep the prototype of the function enqueue_ldpc_dec_one_op_cb() compatible with such usage. 
I believe this is a good practice here. Let us know if you are not convinced. 
Thanks
Nic

> 
> > +			rte_bbdev_log(INFO, "Corner case may require deRM
> pre-processing");
> > +		}
> > +
> >   		fcw = &desc->req.fcw_ld;
> >   		q->d->fcw_ld_fill(op, fcw, harq_layout);
> >
> > @@ -3721,7 +3770,7 @@ acc100_enqueue_ldpc_dec_cb(struct
> rte_bbdev_queue_data *q_data,
> >   			ops[i]->ldpc_dec.n_cb, ops[i]->ldpc_dec.q_m,
> >   			ops[i]->ldpc_dec.n_filler, ops[i]-
> >ldpc_dec.cb_params.e,
> >   			same_op);
> > -		ret = enqueue_ldpc_dec_one_op_cb(q, ops[i], i, same_op);
> > +		ret = enqueue_ldpc_dec_one_op_cb(q, ops[i], i, same_op,
> q_data);
> >   		if (ret < 0) {
> >   			acc_enqueue_invalid(q_data);
> >   			break;